import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int n = in.nextInt();
        int[] prices = new int[n];
        for (int i = 0; i < n; i++) {
            prices[i] = in.nextInt();
        }
        int mixBuy = prices[0];
        int maxProfit = 0;
        for (int i = 0; i < n; i++) {
            if(prices[i] <= mixBuy){
                mixBuy = prices[i];
                continue;
            }else {
                maxProfit += prices[i] - mixBuy;
                if(i < n - 1){
                    mixBuy = prices[i];
                }
            }
        }
        System.out.println(maxProfit);
    }
}